Manufacture of metal ingots and castings



Feb. 23, 1960 -R. c. EDMONDS L 2,925,637

MANUFACTURE OF METAL INGOTS AND CASTINGS Filed March 29, 1957 2Sheets-Sheet l lu l Ill a21 I30 dimz [k M M, m, mwfw Feb. 23, 1960 c,EDMONDS ET AL 2,925,637

MANUFACTURE OF METAL INGOTS AND CASTINGS Filed March 29, 1957' 2Sheets-Sheet 2 Erma/Mora I @M, M01454 MANUFACTURE OF METAL INGOTS ANDCASTINGS Robert Charles Edmonds, Nechelis, Birmingham, and AlanKeyworth, Shelfield, England, assignors to Foundry Services Limited,Birmingham, and John Knowles & Co. Limited, Woodville, near Burton-on-Trent, England Application March 29, 1957, Serial No. 649,388 Claimspriority, application Great Britain April 5, 1956 6 Claims. (Cl. 22147)The present invention relates to the manufacture of metal ingots andcastings and in more particularly concerned with the casting of steeland other metals in ingot form.

In producing metal ingots, it is customary practice, in order to avoidthe adverse effects of uneven cooling of molten metal when poured intoan ingot mould, to employ low thermal conductivity refractory tiles toprovide heat insulation, either by lining the top portion of the ingotmould or by being fitted into a separate ingot head box or hot top whichis located on top of the mould. It has been known for a considerabletime that both the yield and soundness of ingots produced in such mouldsare increased if the refractory tiles are pro-heated prior to pouringthe ingot. Attempts have also been made to employ, instead of tileswhich only have heat insulating properties, tiles or other mouldedshapes such as sleeves made of exothermic material, which set up aheat-producing reaction in contact with the molten metal and therebydelay cooling of the adjacent part of the poured ingot. Exothermicmixtures which can be used in this manner are described in United StatesPatent No. 2,591,105 and in British Patents Nos. 627,678, 774,490,774,491, 769,719 and 722,273.

Although such a technique has been utilised on a production scale, itsapplication is limited, particularly for ingots of the inherently cheapmetals, since the cost of the exothermic materials can outweigh theadvantages of increased ingot yield, increased soundness of ingot and,possibly, increase in the number of ingots produced per ladle of metal.Also, and this is of great importance, the efliciency of the exothermiccompounds is reduced, since the fabricated exothermic tiles and similarshapes come into contact with the high thermally conducting metal of theingot mould or hot top. This results in much of the heat evolved fromthe exothermic material being wasted instead of being utilised forsuperheating the tile or similar shape and delaying the solidificationof the ingot head metal.

Copending United States application Serial No. 563,465, filed February6, 1956, now abandoned, discloses the use of a shaped article for usewith an ingot mould or other metal casting mould comprising an outersurface, namely that surface which does not come into contact with themolten metal, constituted by a heat insulating and inert material,whereas the inner surfaces, which come into contact with the moltenmetal, are composed of a mouldable exothermic material, preferably suchas described in British Patent No. 627,678 or in any of the copendingapplications referred to above. Such combined shapes are more efiicientthan shapes made solely from the exothermic material, or, of course,solely from the backing material; this increased efiiciency enablesconsiderable economies to be made in the application of exothermicmaterials for the feeding of both castings and ingots.

For a large number of applications, particularly in the ingot field, thedouble-layer and occasionally triple-layer shapes of exothermic andrefractory materials are equivalent to plane or substantially planetiles. These tiles, with a surface layer of exothermic materials, arevery convenient for insertion into typical ingot head boxes or ingotmoulds. In fact, they are used in substantially the same way as therefractory and sometimes insulating tiles commercially available foringot production.

It has been found, however, that composite tiles of exothermic andinsulating refractory material sometimes suffer from certaindisadvantages in practice. Thus, bonded exothermic materials are ofconsiderably lower strength than the normal refractory/insulating tilesused for ingot production and abrasion of the exothermic facing layer ofthe composite tiles can occur during their insertion into a head box orrecessed ingot mould. Such abrasion can result in the introduction ofparticles of exothermic materials into the ingot mould with thepossibility of inclusions in the resultant ingot. In addition, abrasionbetween two adjacent tiles on insertion into either head box or recessedmould can result in a cavity or gap between the two tiles which might bepenetrated by the molten metal during the filling of the ingot mould,with increased danger of restricting the contraction of the ingot andconsequently the formation of hot tears or cracks in the ingot.

It is an object of the present invention toprovide such shapes in a formin which these disadvantages are overcome or materially reduced.

More specifically, the primary object of this invention is to provide animproved composite exothermically reacting tile or like shape for use inlining hot tops such as head boxes and recessed ingot molds.

A further object of this invention is to provide heat producing tiles ofthe foregoing type for lining hot tops which overcome the diificultiesof inclusions in the metal cast in the mold resulting from fragments ofexothermically reacting material which break away from the tiles whenthey are mounted in place.

Still another object of the invention is to provide an improved heatproducing tile of the above character which is easily handled, shipedand stored while remaining strong and dry during storage prior to use.

According to the present invention, a shaped article in the form of atile, slab, brick or the like for use with an ingot mould or other metalcasting mould, comprises an outer body, which does not contact themolten metal and which is constituted by a heat insulating and inertmaterial, and an inner layer, for contacting the molten metal, which isconstituted by a mouldable exothermic material, the article having sidesurfaces over at least a part of its periphery which, in use, contactthe side surfaces of other said shaped articles, said side surfacesbeing constituted substantially wholly by the heat insulating inertmaterial, whereby contact between the exothermic material of adjacentsaid shaped articles is reduced or avoided.

Preferably the heat insulating inert material is in the form of aquadrilateral tile having two opposite upstanding sides and theexothermic material is located in the channel thus present in the tileor the heat insulating material is in the form of a quadrilateral tilehaving four upstanding sides and the exothermic material is located inthe recess thus present in the tile.

The ease of handling of composite exothermic/refractory tiles is greatlyincreased by using recessed tiles in whicha mouldable exothermicmaterial can be readily formed and then dried in situ. Such recessedtiles may have re-entrant portions, such as typically dove-tailed,rebate or grooved shapes at their edges, to accommodate the exothermicmaterial and to lock or key it mechanically to the tile. Consequently,on insertion of the tiles into the hot top such as a head box orrecessed ingot mould in juxtaposition to form a lining, only the hardside surfaces of the refractory material come into contact with eachother and there is no danger of abrasion of the exothermic material. Itwill be appreciated that where only one tier of tiles is required, theheat insulating and refractory material of each tile need only be ofchannel shape and disposed with the channels vertical, so that the upperand lower end surfaces of the tiles include exposed exothermic material,but, where more than one tier of tiles is used, it is desirable for allside surfaces thereof to be constituted by the refractory material.

These shapes have the additional advantages that it is extremely easy toinsert layers of highly insulating materials into recessed portionsbetween the refractory backing and exothermic material; thus a layer ofsuch insulators as vermiculite can be spread on to the tile, oralternatively insulating inserts may be readily stuck on to the recessedface of the tile prior to ramming the mouldable exothermic material intoposition. Such triplex shapes, as described in the above mentionedcopending application Serial No. 563,465, can be of even greaterelficiency than the duplex shapes.

Finally, it has been found possible with such recessed tiles to overcomeone other difiiculty of exothermic/refractory tiles. Exothermicmaterials tend to absorb water and consequently loss strength onstanding and the duplex tiles can eventually become unsatisfactory forfoundry usage if stored in a humid atmosphere for long times. Theserecessed tiles make it readily possible to prevent moisture pick-up bysealing a layer of wax paper or some similar water repellant material onthe facing edge of the refractory tile so that the exothermic materialis completely or substantially covered.

The accompanying drawings, in which the figures each show in perspectiveview one form of tile, illustrate diagrammatically specific examplesaccording to the invention but are not to be regarded as limiting theinvention in any way:

Fig. 1 shows a tile in which the refractory portion 10 has a dovetailchannel therein for receiving the exothermic material 11, the tile beingbevelled on all sides.

Fig. 2 shows a tile in which the refractory portion .11 has aninverted-T-section channel therein for receiving the exothermic material13, the tile being bevelled at its ends.

Fig. 3 shows a triplex tile in which the refractory portion '14 has acomplex channel therein, forming a rectangular section channel forreceiving a highly insulating material 15 and a dovetail portion forreceiving the exothermic material 16.

Fig. 4 shows a triplex tile in the form of a par tcylindrical surface.The refractory portion 17 has an inverted-T-section channel thereincoaxial with the cylinder formed from a number of the tiles in the lowerpart of which a layer of highly insulating material 18 is disposed. Inthe remainder of the channel, an exothermic material 19 is provided soas to have rabbeted portions as at 20.

Fig. shows a flat, recessed tile of rectangular form in which therefractory portion 21 forms all four sides of the tile, an undercutrecess in the front surface being filled with exothermic material 22.Over the whole of this front or outer surface, a sheet of wax paper 23is applied for protecting the exothermic material 22 during storage ofthe-tiles Suitable compositions of heat-insulating and inert materialare as follows:

Percent Grog, sand, crushed firebrick or any other granular refractorymaterial -90 Binder (such as sodium silicate, dextrine gum or sulphitelye) Clay or fireclay To this is bonded, to form a shaped article suchas a 1. A hot top having an inserted lining composed of a plurality oftiles each of which comprises a body of heatinsulating material havingrecessed therein a layer of moldable exothermically reacting material,at least two opposite side portions of the tile consisting wholly ofsaid insulating material, the tiles being inserted in juxtaposition toconstitute a lining and making edge to edge contact at the said sidesconsisting wholly of said heat insulating material.

2. The hot top defined in claim 1 wherein each tile has two oppositeupstanding sides and exothermically reacting material being located inthe channel thus defined in the tile.

3. The hot top defined in claim 1 wherein each tile has four upstandingsides and exothermically reacting material being located in the recessthus defined in the tile.

4. The hot top defined in claim 1 wherein each tile has four upstandingsides and exothermically reacting material being located in the recessthus defined in the tile, the said upstanding sides of the tile havingre-entrant angles whereby the exothermically reacting material is keyedto the tile.

5. For use in lining a hot top, a plurality of tiles each of whichcomprises a body of heat-insulating material having recessed therein alayer of moldable exothermically reacting material, at least twoopposite side portions of the tile consisting wholly of said insulatingmaterial, the tiles being inserted in juxtaposition to constitute alining and making edge to edge contact at the said sides consistingwholly of said heat insulating material.

6. The tiles defined in claim 5 wherein each tile has a layer ofwater-repellent material over the outer surface of the exothermicallyreacting material.

References Cited in the file of this patent UNITED STATES PATENTS

